Grafted Photo-Polymerized Monolithic Column

Abstract

The present invention relates to the fabrication of a grafted, UV photo-polymerized silica-based monolithic column and the use of such column for the extraction of DNA. In one embodiment, a method is provided for fabricating a silica-based monolithic column, wherein a vessel is filled with a polymerization mixture that is formed into monolithic solid phase for DNA extraction through in situ photo-polymerization.

Description

[0001]The present invention claims priority from U.S. Provisional Application Ser. No. 60 / 656,998, filed Feb. 28, 2005, and from U.S. Provisional Application Ser. No. 60 / 740,977, filed Nov. 30, 2005, both of which are incorporated herein by reference herein in their entirety.BACKGROUND OF THE INVENTION[0002]DNA extraction is a sample preparation technique often utilized in clinical and forensic applications to purify and concentrate DNA for genetic analysis from small volume samples that typically are dilute or biologically complex, e.g. blood. Significant effort has been invested in the last two decades into devising methods that reduce the amount of sample required for genetic analysis, often to address the needs of clinical and forensic communities. One such method has involved adapting traditional genetic analysis methodologies to a microscale format. The miniaturization of sample preparation techniques, including DNA extraction, has been included in the move towards microscale ...

AI Technical Summary

Benefits of technology

[0012]The silica-based monolithic column described in the present invention possesses enhanced capacity and efficiency for extraction, allowing for an increase in the yield of nucleic acid extracted from very low volume samples. Additionally, the silica-based monolithic column described in the present invention allows for nucleic acid to be eluted from the column using a minimal volume of a low ionic strength buffer, which further allows direct PCR analysis of the extracted nucleic acid without further sample cleaning steps, unlike the elution buffers used with commercial monolithic affinity columns which typically have a high salt concentration and / or high pH. Furthermore, the silica-based monolithic column described in the present invention allows for precise placement of the monolithic column in a capillary or other microdevice, such as a microfluidic microchip.

Problems solved by technology

Issues of reproducibility, however, have resulted from the inability to completely immobilize the silica beads within the column (Wolfe et al.

First, the additional processes involved in filling microchannels on devices such as microfluidic chips with silica beads increases the fabrication time for such solid phase columns.

Second, when using microfluidic chips for extraction, chip-to-chip extraction reproducibility, while somewhat improved through bead immobilization, continues to be a significant problem.

Third, while the surface area available for DNA binding is enhanced by decreasing the bead diameter, smaller diameter beads (e.g., 5 μm) are more difficult to contain, resulting in higher back pressures which limit μSPE columns in microdevices to relatively low flow rates and low binding capacity.

While this increases the surface area for DNA binding and provides a regular array for reproducible chromatography, complex fabrication requirements and cost make these microdevices less attractive.

Moreover, a large volume of elution buffer (greater than 50 μL) is required to elute the bound DNA from the columns of these microdevices, creating potential difficulties with downstream processing (e.g., PCR).

DNA purification and separation have also been performed on bacterial and yeast genomic DNA in these columns; however, these columns showed low extraction efficiencies and required a high salt and high pH buffer for DNA release, which has been found to interfere with downstream processing, e.g. PCR.

Moreover, thermally-induced polymerization does not ensure the accurate placement of monolithic columns within the architecture of microdevices.

While silica-based monolithic columns have been found to be functional for binding and extracting DNA, the use of certain silica-based monomers as part of the initial polymerization mixture has been problematic.

Tetraethylorthosilicate (TEOS)-based monolithic columns have been found not to yield extraction efficiencies comparable to columns created with silica beads, due mainly to the difficulty in controlling pore size within such silica-based sol gel columns which, in turn, inhibits fluid flow.

Anal. Chim. Acta 2003, 500, 223-236, were produced using tetramethoxyorthosilicate (TMOS) monomers and a porogen to provide the appropriate pore size, but these columns could not easily be localized within microdevices.

None of the methods described above provides the important advantages of the fabrication method for a grafted UV photo-polymerized silica-based monolithic column.

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